If your roof was damaged and you do not want help from any professionals and want to do it yourself, here are some tips on preparing to re-roof old construction:
If you will be reroofing over roll roofing or asphalt shingles, first remove loose nails. Loose or broken asphalt shingles should be removed or nailed down. Split and nail wrinkles in rolls. Buckled shingles usually indicate protruding nails or warped deck boards. Drive down such nails and re-nail warped boards.
If re-roofing over old wood shingles, remove loose and protruding nails and re-nail loose shingles. Split badly warped shingles and nail down segments, and replace missing shingles with new ones. It is especially important to replace any shingles at the rake that are in bad condition because the rake is vulnerable to damage from high winds.
When shingles and trim at the eaves and rakes are badly weathered, and the work is in a location subject to high winds, shingles at the eaves and rakes should be cut back far enough to allow use of 4 to 6 inches of nominal 1-inch thick wood boards. Nail the boards firmly into place, allowing the outside edges to project beyond the edges of the deck the same distance as did the wood shingles. If old shingles are badly curled or turned at butts, a smooth surface and solid nailing base can be gained by nailing a feathering strip along the butts. These strips are best beveled at the lower edge.
Cedar shakes, unlike wood shingles, must be removed before re-roofing with asphalt shingles.
To improve appearance at eaves and rakes and to provide better alignment of asphalt shingles, better nailing, and better wind resistance, install a 1-inch by 4-inch or 1-inch by 6-inch wood strip at the eaves and rakes by removing enough old shingles to make room. Projection of the strip should be the same as that of the old wood shingles. Use suitable drip edges and eaves flashing strips. Asphalt shingles, wood shingles, and original felts may be removed with flat-edged shovels. Use a pry bar to remove the soil stack and vent flashing before re-roofing. Also, remove debris and waste materials from the deck and sweep it clean.
When measuring existing roofs before re-roofing, it is advisable to measure both rakes. It’s not unusual to find a difference of several inches between rakes on the same roof. By discovering this before applying new shingles, the applicator can compensate for the difference before it is noticeable, by trimming the old wood shingle up to the chalk line.
If the condition of the roof, deck, or supports requires the removal of old roofing, repair the roof framing so that it is strong. Remove loose or protruding nails and re-nail sheathing at new nail locations, remove warped or rotted sheathing and replace with new, and fill in sheathing where necessary. Cover large cracks, loose and pitchy knots, and knot holes with sheet metal.
Before starting to re-roof, carefully inspect adjacent parts of the building for defects. Repair or replace rotting or deteriorated woodwork. Point up chimneys if needed. Clean, rebuild, or reline gutters, and make sure of adequate under-roof ventilation. Just before applying the new roof, clean all debris from the deck surface.
Once repairs are completed and the deck is prepared, follow the steps for new construction. Apply No. 15 asphalt-saturated felt to the deck, as in new construction. Snap horizontal and vertical chalk lines to ensure that the shingles will be correctly aligned and applied in the recommended manner. Install flashing as needed and apply drip edges at eaves and rakes.
Because nails should be long enough to penetrate through the roofing material and at least ¾ inch into the wood deck, or through a plywood deck, nails used for re-roofing are longer than nails used in new construction or in re-roofing where the existing roofing material has been removed. For re-roofing over old wood shingles, use 1 ¾ inch bails. For re-roofing over asphalt roofing, nails 1 ¼ inches to 1 ½ inches long. For tearoffs, 1 inch or 1 ¼ inch nails are recommended, the same as is new construction.
However, if you are not that experienced in construction then you should always hire a construction recruitment agency for such tasks. Doing them on your own can be dangerous and you can hurt yourself quite badly in this process as well.